The relationship between the level of vitamin D and ruptured intracranial aneurysms among patients with high sun exposure

Non-traumatic subarachnoid hemorrhage (SAH) accounts for 3–5% of acute strokes. Intracranial aneurysm is the most common cause of non-traumatic SAH. Vitamin D influences the cardiovascular system, including the formation and rupture of cerebral aneurysms. To evaluate the serum vitamin D level in patients living in the tropical zone who suffered aneurysmal subarachnoid hemorrhage and its correlation with demographic and neurological characteristics. This is an analytical cross-sectional study to assess the serum level of vitamin D in a study population of 99 patients treated and diagnosed with aSAH in a public hospital in Recife-PE over a period of 12 months. In the study sample, composed of individuals with high sun exposure due to the lifestyle they lead in a tropical region, we observed hypovitaminosis D (85.9%), with a median of 19.9 ng/ml, although the majority of individuals are skin with high concentration of melanin (Fitzpatrick skin type IV and V). In addition, rates of sun exposure are high to all patients (Solar Index 9.03 P50). Most individuals were female (79.8%); there was no statistical difference in solar exposure/solar index between genders. As for the neurological repercussions, there was no statistical relevance in the clinical prognostic scales evaluated. As the sample was composed mainly of individuals whose economic activity is agriculture, the values of solar index found are vastly higher than those of other studies conducted in high latitude regions. In line with the literature review, some aspects were raised with the objective of justifying such findings that go from the base of the poor diet of these individuals, the increase of melanin in the skin and genetic alterations that directs us to possible mechanisms of natural photoprotection to high sun exposure. Thus, we had a vast majority (85%) of hypovitaminosis D, which in fact makes us wonder if there is any influence of calcitriol on vitamin D receptors in vascular walls and in the cardiovascular system as a whole, which influence bleeding events of this nature. As for the neurological repercussions, measured using assessment scales (Glasgow coma scale, WFNS scale, Hunt–Hess and Fisher's tomographic scale) there was no significant difference in the results. As it is only a descriptive study, the causal relationship of the facts cannot be established. However, in a population exposed to high sun exposure and affected by aneurysmal SAH, there is a significant rate of hypovitaminosis D, which supports the hypothesis that vitamin D plays a role in vascular pathologies, such as cerebral aneurysms and SAH.


Inclusion criteria
Patients of both genders, aged 18 years or older, who had suffered from aneurysmal subarachnoid hemorrhage (aSAH), diagnosed through invasive or non-invasive neuroimaging examinations (magnetic resonance angiography or angiography) at a major hospital in Recife, Brazil, a reference in Neurosurgery, during the 12-month study period (May 2021 to May 2022) were included.

Exclusion criteria
Exclusion criteria were as follows: (1) a known family or personal history of spontaneous aSAH or arteriovenous malformations based on previous imaging examinations; (2)

Vitamin D measurement
Vitamin D sufficiency was estimated by measuring 25-hydroxyvitamin D (25[OH]D or calcidiol) concentrations.The ideal serum concentration of 25(OH)D for bone health is controversial, with most experts agreeing that levels below 20 ng/mL are not ideal for bone health 55,56 .However, ideal serum concentrations of 25(OH)D for extra-skeletal health have not been well established yet.Given the controversy around ideal serum concentrations of vitamin D, the definitions of sufficiency, insufficiency, and deficiency of vitamin D are only approximate.In this study, we followed the Endocrine Society's 2011 guideline, where circulating concentrations of 25(OH)-D were divided into three subgroups to categorize vitamin D status in adults: deficient (< 20 ng/ml), insufficient (20-29 ng/ml), and sufficient (≥ 30 ng/ml), encompassing the concept of hypovitaminosis D, which includes both deficiency and insufficiency.

Results
The clinical and demographic characteristics of the sample are shown in Table 1.A questionnaire was administered to 110 patients diagnosed with ruptured intracranial aneurysms.A total of 11 individuals were excluded, resulting in a sample of 99 patients.Among the excluded individuals, nine were excluded based on the exclusion criteria, and two were excluded due to centrifugation and storage failure of the biochemical vials for vitamin D analysis.The majority of individuals were female (79.8%) with a mean age of 53.22 ± 14.53 years.Most patients had a normal body mass index (BMI).Concerning comorbidities and risk factors, 10.1% of the sample had diabetes mellitus and 14.1% reported alcohol consumption.Systemic arterial hypertension was present in 54.5% of patients and 33.3% of the sample smoked.
Regarding skin phototype, it is noteworthy that 60.6% of the sample had skin phototypes ranging from IV to VI, with skin phototype IV (39.4%) contributing the most, consistent with previous studies conducted on a similar population in Brazil 56 .Although ideal serum values for vitamin D levels remain controversial, especially when considering different study populations, we chose a cutoff point for vitamin D sufficiency of serum values ≥ 30 ng/ml, as established by the Endocrine Society.Hypovitaminosis D was defined as serum values < 30 ng/ml.In our sample, a significant portion of individuals had vitamin D hypovitaminosis (85.9%), with a median of 19.9 ng/ml.This finding is impactful, especially when combined with the fact that most individuals had Fitzpatrick skin type IV or V and high rates of sun exposure (SI 9.03 P50).There was no difference in the solar index values between genders (males: 13.26 ± 10.26; females: 10.39 ± 7.9; p = 0.292).
The neurological characteristics of the sample are presented in Table 2. Regarding neurological prognosis scales for aSAH, the samples had a mean score of 2.37 ± 0.98 on the HH scale, 2.05 ± 1.27 on the WFNS scale, and 13.36 ± 2.50 on the GCS.The majority of the sample had a Fisher grade of IV (44.4%) on the cranial computed tomography, followed by Fisher grade III (35.35%).
When comparing the results of these scales and the serum level of vitamin D to assess patient prognosis, there was no significant correlation.In the prognostic evaluation, there was also no statistically significant correlation with hypovitaminosis D in relation to the presence of delayed cerebral ischemia (DCI).
Regarding the locations of ruptured aneurysms, the majority were in the internal carotid artery (ICA), followed by the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior circulation (PC).There was no difference in the locations between individuals with hypovitaminosis and patients without vitamin D hypovitaminosis.Patients with hypovitaminosis D (< 30 ng/ml) had slightly larger aneurysms, but this finding was not statistically significant.
Therefore, although the sample comprises a significant portion of individuals with vitamin D hypovitaminosis, this status did not appear to impact the degree of clinical or neurological impairment resulting from aSAH.
As an additional finding, it was observed that the initial HH grade correlated with morbidity, being the main parameter, with the majority of patients with HH < 3 having a favorable outcome (ERm < 3; Table 3).
Three patients in the sample died before the treatment of the ruptured aneurysm.With respect to treatment, 57.57% were treated with microsurgery, with 54 undergoing clipping and three undergoing bypass surgery, and 38 (38.4%) were treated with endovascular intervention (Table 4).

Demographic characteristics and endocrinological features
The sample consisted of 99 patients, which is a significant number and indicates a high demand at the hospital over an 12-month period.Most of the patients in the sample were female (79.8%) and middle-aged (53.22 ± 14.53 years old).These demographics are similar to those commonly described in populations with ruptured aneurysms [34][35][36] .Some well-established risk factors for aneurysm formation and rupture, such as smoking and hypertension, were present in a substantial portion of the sample (33.3% and 54.5%, respectively).The study's sample was from the state of Pernambuco, located in the northeastern region of Brazil, in a tropical climate zone at a low latitude (approximately 8° 3′ 15″ South).In this region, sunlight strikes the surface almost directly year-round, resulting in minimal variation in day and night duration.Unlike temperate climates, there are no well-defined seasons in this area.Therefore, the high levels of ultraviolet (UV) solar radiation (≥ 8) or extreme (≥ 11) are a characteristic feature throughout the year.
The Hospital da Restauração, where the data was collected, exclusively serves patients from the brazilian Unified Health System (SUS) and is a state reference center for neurology and neurosurgery, receiving a high annual volume of patients.
Most of the patients treated come from low-income backgrounds with limited education, many referred from rural areas where their primary occupation involves outdoor agricultural work, resulting in high sun exposure.Some studies have evaluated serum vitamin D levels in individuals from different professions, demonstrating that individuals who work indoors with limited sun exposure are at a higher risk of developing vitamin D deficiency.This is in contrast to the study's population, which should have lower risk due to significant sun exposure during their work [58][59][60][61] .Therefore, this study has a unique sample in terms of high solar index (SI) values.
Regarding ethnic characteristics, there was a high prevalence of skin phototypes with a high melanin concentration (Fitzpatrick skin type III or higher).This ethnic characteristic, common in northeastern Brazil, differs significantly from the populations in most previous studies, which were conducted in temperate climate regions [34][35][36] .Several studies have demonstrated that individuals with darker skin generally have lower absolute levels of vitamin D than Caucasians.Melanin's interference with vitamin D production activity can contribute to this phenomenon.Melanin competes for ultraviolet B (UVB) photons (220-390 nm) on the skin, hindering most of them from being used for the photolysis of 7-dehydrocholesterol (7-DHC) and the subsequent formation of pro-vitamin D3, the initial reaction of the classical pathway.Individuals with higher melanin concentration in their skin require longer UVB sun exposure to achieve the same serum level of 25-hydroxyvitamin D [25(OH) D] compared to those with lower melanin concentration.Some studies show that individuals from South Asia, who typically have skin phototype V, need long exposure periods (about 25-40 min) with a large area of exposed skin (35%) to reach average annual serum concentrations of 25 nmol/L, which is similar to natives of England who achieve such levels with significantly lower solar indexes 62 .
Moreover, it is important to note that the majority of vitamin D (about 80%) in the body is produced endogenously through sunlight exposure, as described earlier.Foods rich in vitamin D are primarily fatty fish from cold, deep waters or those containing ergosterol (vitamin D2) present in fungi.Neither form is easily accessible to the majority of the population, especially the one in this study, which is a predominantly low-income population.Furthermore, no patient in the study was using vitamin D supplementation.
Even in areas with high sun exposure, some studies have reported a high prevalence of vitamin D deficiency, indicating that sunlight exposure alone is insufficient to achieve adequate vitamin D levels in the majority of individuals 63 .Certain genetic variants may lead to different responses of serum 25-OHD to pro-vitamin D. Minor alleles of CYP2R1 (belonging to the cytochrome P450 subfamily IIR1 and encoding hepatic 25-hydroxylase),  64 .
In light of this, our primary hypothesis justifying the substantial prevalence of hypovitaminosis D even in areas with high sun exposure is the presence of polymorphisms in genes activating 25-OHD, likely constituting a natural selection characteristic favoring high sun exposure to avoid overproduction or intoxication.Some studies have observed a high prevalence of vitamin D deficiency even in areas with high sun exposure and we particularly highlighting the research demonstrating hypovitaminosis D in a population from the same city with similar demographic characteristics as our current study 65 .The highlight of our paper is that it revealed even lower serum vitamin D levels in patients with SAH.

Neurological characteristics
A high rate of hypovitaminosis D was observed in the sample of patients with ruptured aneurysms studied (85.9%).This finding aligns with recent studies that suggest that vitamin D deficiency could be associated with cerebral aneurysms [34][35][36] .A recent controlled study also demonstrated that vitamin D levels are independently associated with cerebral aneurysms 37 .Additionally, another study by the same authors demonstrated an association between hypovitaminosis D and aneurysm rupture 66 .
To characterize the neurological aspects of our sample of patients with aSAH, several classic scales were applied.The sample had an average score of 2.37 ± 0.98 on the HH scale, 2.05 ± 1.27 on the WFNS scale, and 13.36 ± 2.50 on the GCS.These scales play an important role in the prognosis of patients with aSAH.In our study, it was observed that the HH grade correlates with morbidity, with statistical significance when compared to the modified Rankin scale.This finding is consistent with other studies in the literature 67,68 .
Although there seems to be a relationship between hypovitaminosis D and aneurysm formation/rupture, there are few studies that demonstrate a relationship between the degree of vitamin D deficiency and patient prognosis.A recent study of 40 patients with aSAH showed a high prevalence of vitamin D deficiency among them, but no difference in clinical outcomes 36 .
In our study, when we compared the results of the prognostic scales for aSAH and the modified Rankin Scale with the levels of vitamin D deficiency (< 20 ng/ml), insufficiency (20 to < 30 ng/ml), or sufficiency (≥ 30 ng/ml), we also did not find a significant correlation with patient prognosis.
Regarding the correlation between the size of the aneurysm and vitamin D deficiency, some epidemiological studies reported a correlation between the size of extracranial artery dilation, aortic aneurysms, and vitamin D deficiency [69][70][71][72][73][74] .However, there are no studies yet demonstrating this correlation with cerebral aneurysms.In our study, we observed that patients with hypovitaminosis D (< 30 ng/ml) had slightly larger aneurysms compared to patients with sufficient vitamin D, but this finding did not reach statistical significance.
Regarding the locations of the ruptured aneurysms, the majority were in the internal carotid artery (ICA), followed by the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior circulation (PC).There was no difference in the location between individuals with hypovitaminosis and those without hypovitaminosis D, although a detailed subgroup analysis was not conducted.
As for the presence of DCI, some studies provide evidence of an association between vitamin D deficiency, the frequency of cerebral vasospasms, and the overall outcome of patients after subarachnoid hemorrhage 36,[75][76][77] .Additionally, the therapeutic utility of vitamin D has been demonstrated in animal models, leading to a reduction in the incidence of DCI, serving as a predictive indicator, a prevention method, and/or a treatment option after spontaneous SAH.However, these results have not yet been fully investigated in human studies 78,79 .
In our study, there was no statistically significant correlation between the presence of DCI and hypovitaminosis D. Similar results were obtained in a recent study of 33 patients, showing a higher proportion of patients with aSAH had vitamin D deficiency, but there was no difference in the occurrence of vasospasm or overall outcome 36 .
Furthermore, among the patients analyzed, three patients from the sample died before the treatment of the ruptured aneurysm.Regarding the treatment of the sample, 57.57% underwent microsurgery, with 54 undergoing clipping and 3 undergoing bypass technique, while 38 (38.4%) were treated with endovascular intervention (coilling).It was also observed that among the patients who underwent microsurgery, there was a better morbidity outcome assessed by the modified Rankin Scale.This could be attributed to the fact that the majority of these patients had a HH grade < 3, and the patients allocated for endovascular procedures were older.

Study limitations
There are several limitations in our study.The COVID-19 pandemic was a limiting factor, primarily causing delays in data collection for over a year after approval by the Ethics Committee.Additionally, the pandemic and home isolation may have directly influenced the sunlight exposure of these patients in the months leading up to data collection.
The fact that this was an uncontrolled study conducted at a single center is another limitation.However, it's important to note that the study's original objective did not include control groups.On the other hand, this study's strength lies in its inclusion of a significant number of individuals (n = 99) from a low-latitude region, unlike most studies that were conducted in temperate climate regions.
To our knowledge, this is the first study to investigate the rate of vitamin D deficiency in patients with ruptured aneurysms in a tropical region, specifically in northeastern Brazil.

Conclusion
Since this is only a descriptive study, a causal relationship cannot be established.Nevertheless, a significant percentage of a population exposed to high levels of sunlight and affected by aSAH had hypovitaminosis D. Although recent studies demonstrate a high prevalence of vitamin D deficiency even in areas with high sun exposure, the highlight of our paper is that it revealed even lower serum vitamin D levels in patients with aSAH.This is a broad topic, and there are still relatively few studies on it, especially in regions between the tropics.While there are limitations in the current studies, advances in research show a promising correlation between hypovitaminosis D and cerebral aneurysms.Therefore, more research should be conducted, both pre-clinical and clinical, to further investigate this relationship.
chronic kidney or liver disease; (3) treatment with vitamin D for any reason; (4) pregnancy at the time of the analysis; (5) previous use of oral or injectable anticoagulants.

Figure 1 .
Figure 1.Low Latitude of Recife, Pernambuco, Demonstrated on the World Map.

Table 1 .
Demographic and clinical characteristics of the sample.
a Using the Student's t test with equal variances.b Using the Mann-Whitney test.c Using Fisher's exact test.d Using Pearson's chi-square test.*Statistically significant difference at the 5.0% level.Indicators Vit D <

Table 2 .
Neurological characteristics of the sample.a Using the Student's t test with equal variances.b Using the Mann-Whitney test.c Using Fisher's exact test.d Using Pearson's chi-square test.e Using Kruskal Wallis test.*Statistically significant difference at the 5.0% level.

Table 3 .
Evaluation of the Hunt Hess score according to the mRS score.DiscussionSeveral studies in temperate climates have demonstrated both the seasonality of aSAH and vitamin D, which both show a higher prevalence during colder periods.During colder seasons, there is less sunlight exposure, which may result in reduced vitamin D activation 57 .To date, all studies of sSAH and vitamin D have been conducted in temperate climate countries.This study is the first to evaluate serum vitamin D levels in patients with ruptured cerebral aneurysms in a tropical region near the equator, specifically, northeastern Brazil.

Table 4 .
Evaluation of Hunt Hess and mRS scores according to the aneurysm management.a Using Fisher's exact test.*Statistically significant difference at the 5.0% level.such as rs10500804, and specific group complement, encoding VDR and DBP, such as rs4588 and rs7041, are associated with a reduced response of serum 25-OHD to UV radiation.Consequently, there may be lower efficacy of sunlight exposure in preventing and treating vitamin D deficiency Vol.:(0123456789) Scientific Reports | (2024) 14:3555 | https://doi.org/10.1038/s41598-024-53676-ywww.nature.com/scientificreports/